1. Field of the Invention
The present invention relates to a fluid-tight molten metal casting device on a pressure moulding machine applicable to casting in contact with a gas or in a vacuum.
2. Description of the Prior Art
A known pressure casting installation of an industrial kind comprises: a holding furnace or a crucible containing the molten metal to be cast and a means for injecting the molten metal typically constituted by a cylinder provided with a piston. Means such as a supply pipe for feeding the cylinder brings the molten metal from the crucible into the injection cylinder. For low pressure casting, the means for injecting the metal in the mould and the feed means can be combined.
At present, a known device for adjusting the casting on machines for moulding under pressure with a cold chamber comprises:
A crucible containing the molten metal arranged below and to one side of a mould, a pump immersed in the molten metal, an ascending mould feed pipe, a junction on the supply pipe, a level determining tank connected to a return pipe for returning the molten metal to the crucible.
In this device, the said junction connects the level-determining tank to the feed pipe and thus determines at all points of the latter a level of metal defined with precision.
When the metal to be cast is particularly reactive, for example in contact with atmospheric oxygen, it appeared desirable to constitute a casting device which is sufficiently fluid-tight for the filling of the mould to be possible in contact with a predetermined gas or else in a vacuum.
When a vacuum has been set up in the mould by means of a vacuum pump, a part reproducing with great exactitute the finest designs of the mould is obtained.
When the mould undergoes subsequent filling by means of a gas having a suitable composition, surface treatment can be effected on the part during casting.
In any case, the maintaining in a vacuum of the crucible containing the metal during the casting operations ensures appreciable degassing of the metal to be cast.